#include <stdio.h>
int main()
{
    int a,s,n,count ;
    a=2 , s=0 , n=1 ,count=1;
    while(count<=7)
    {
        n = n * a;
        s = s + n ;
        count++;
    }
    printf("s = %d\n",s);
    return 0;
}